Add pendulum demo and WGSL support

Introduce a new Pendulum demo (component, template, stylesheet) and wire it into routing and the algorithms list. Extend Babylon canvas API to emit a SceneReadyEvent (scene + engine) and accept a shaderLanguage option in RenderConfig so materials/shaders can target WGSL; update Fractal to consume the new SceneReadyEvent signature. Also add i18n entries for the pendulum demo.

src/assets/i18n/de.json

@@ -441,6 +441,10 @@
       "TITLE": "Fraktale 3D",
       "DESCRIPTION": "3D-Visualisierung von komplexe, geometrische Mustern, die sich selbst in immer kleineren Maßstäben ähneln (Selbstähnlichkeit)."
     },
+    "PENDULUM": {
+      "TITLE": "Pendel",
+      "DESCRIPTION": "Noch ein WebGPU test."
+    },
     "NOTE": "HINWEIS",
     "GRID_HEIGHT": "Höhe",
     "GRID_WIDTH": "Beite"